U.S. patent application number 12/339621 was filed with the patent office on 2009-06-25 for coating compositions and curing method thereof.
This patent application is currently assigned to ETERNAL CHEMICAL CO., LTD.. Invention is credited to Lung-Lin HSU, Sue-Hong LIU.
Application Number | 20090163614 12/339621 |
Document ID | / |
Family ID | 40690271 |
Filed Date | 2009-06-25 |
United States Patent
Application |
20090163614 |
Kind Code |
A1 |
HSU; Lung-Lin ; et
al. |
June 25, 2009 |
COATING COMPOSITIONS AND CURING METHOD THEREOF
Abstract
The invention provides a coating composition comprising a
thermal plastic resin selected from the group consisting of a
polycycloolefin resin, polyester resin, polyacrylate resin, and a
mixture thereof; and a radiation curable resin comprising a
radiation polymer containing at least one mono- or multi-functional
acrylic acid based monomer as a polymerization unit, an oligomer
containing an ethylenically unsaturated functional group, and a
photoinitiator, wherein the radiation curable resin is used in an
amount of 220-1000% by weight on the basis of the weight of the
thermal plastic resin. The invention improves the hardness of the
coating composition, prevent the coated substrate from being
scratched or impaired, and impart the substrate with high
transparency without causing warping problem.
Inventors: |
HSU; Lung-Lin; (Kaohsiung,
TW) ; LIU; Sue-Hong; (Kaohsiung, TW) |
Correspondence
Address: |
LADAS & PARRY LLP
26 WEST 61ST STREET
NEW YORK
NY
10023
US
|
Assignee: |
ETERNAL CHEMICAL CO., LTD.
|
Family ID: |
40690271 |
Appl. No.: |
12/339621 |
Filed: |
December 19, 2008 |
Current U.S.
Class: |
522/40 ; 522/100;
522/111; 522/112; 522/42; 522/46; 522/64; 522/77; 522/78; 522/79;
522/81; 522/83; 522/90 |
Current CPC
Class: |
C08L 33/06 20130101;
C09D 133/08 20130101; C09D 167/00 20130101; C08L 87/00 20130101;
C09D 133/08 20130101; C08L 2666/02 20130101; C09D 167/00 20130101;
C08L 2666/04 20130101 |
Class at
Publication: |
522/40 ; 522/111;
522/112; 522/90; 522/100; 522/46; 522/42; 522/64; 522/79; 522/78;
522/77; 522/81; 522/83 |
International
Class: |
C08F 2/50 20060101
C08F002/50; C08J 3/28 20060101 C08J003/28; C08G 18/67 20060101
C08G018/67; C08G 59/14 20060101 C08G059/14 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 24, 2007 |
TW |
096149732 |
Claims
1. A coating composition comprising: (a) a thermal plastic resin
selected from the group consisting of a polycycloolefin resin,
polyester resin, polyacrylate resin, and a mixture thereof; and (b)
a radiation curable resin comprising: (b1) a radiation polymer
containing at least one mono- or multi-functional acrylic acid
based monomer as a polymerization unit; (b2) an oligomer having an
ethylenically unsaturated group; and (b3) a photoinitiator, wherein
the radiation curable resin is used in an amount of 220-1000% by
weight on the basis of the weight of the thermal plastic resin.
2. The coating composition as claimed in claim 1, wherein the
radiation curable resin is used in an amount of 250-500% by weight
on the basis of the weight of the thermal plastic resin.
3. The coating composition as claimed in claim 1, wherein the
thermal plastic resin has at least one functional group selected
from the group consisting of hydroxy, carboxy, amido, urethano, and
epoxy, and a combination thereof.
4. The coating composition as claimed in claim 1, wherein the
thermal plastic resin is a polyacrylate resin.
5. The coating composition as claimed in claim 1, wherein the
polyacrylate resin contains a polymerization unit derived from
acrylic acid, methacrylic acid, methyl acrylate, methyl
methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate,
butyl methacrylate, iso-butyl acrylate, iso-butyl methacrylate,
iso-octyl acrylate, iso-octyl methacrylate, cyclohexyl acrylate,
cyclohexyl methacrylate, glycidyl acrylate, glycidyl methacrylate,
hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl
acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
2-hydroxypropyl methacrylate, or hydroxypropyl methacrylate or a
mixture thereof.
6. The coating composition as claimed in claim 1, wherein the
thermal plastic resin has a glass transition temperature greater
than 80.degree. C.
7. The coating composition as claimed in claim 1, wherein the
thermal plastic resin has a glass transition temperature of from
80.degree. C. to 250.degree. C.
8. The coating composition as claimed in claim 1, wherein the
thermal plastic resin has an average molecular weight in the range
from 10.sup.4 to 2.times.10.sup.6.
9. The coating composition as claimed in claim 1, wherein the mono-
or multi-functional acrylic acid based monomer is an acrylate
monomer.
10. The coating composition as claimed in claim 9, wherein the
acrylate monomer an acrylate monomer, a methacrylate monomer, a
urethane acrylate monomer, a polyester acrylate monomer, or an
epoxy acrylate monomer.
11. The coating composition as claimed in claim 9, wherein the
acrylate monomer is a methacrylate monomer.
12. The coating composition as claimed in claim 1, wherein the
oligomer having an ethylenically unsaturated group is an acrylate
oligomer selected from the group consisting of urethane acrylates,
epoxy acrylates, novolac epoxy acrylate, polyester acrylates,
acrylates and a mixture thereof.
13. The coating composition as claimed in claim 1, wherein the
oligomer having an ethylenically unsaturated group has a molecular
weight in the range from 10.sup.3 to 10.sup.4.
14. The coating composition as claimed in claim 1, wherein the
photoinitiator is selected from the group consisting of
benzophenone, benzoin, 2-hydroxy-2-methyl-1-phenylpropan-1-one,
2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy cyclohexyl phenyl
ketone, and 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, and a
mixture thereof.
15. The coating composition as claimed in claim 1, wherein the
photoinitiator is benzophenone or 1-hydroxy cyclohexyl phenyl
ketone.
16. The coating composition as claimed in claim 1, further
comprising an anti-static agent selected from the group consisting
of ethoxy glycerin fatty acid esters, quaternary amine compounds,
aliphatic amine derivatives, polyethylene oxide, siloxane, and
alcohol derivatives.
17. The coating composition as claimed in claim 1, further
comprising inorganic particulates selected from the group
consisting of zinc oxide, zirconia, silicon dioxide, titanium
dioxide, alumina, calcium sulfate, barium sulfate, and calcium
carbonate, and a mixture thereof
18. The coating composition as claimed in claim 1, further
comprising diffusion particles selected from those of an acrylate
resin, a methacrylate resin, a styrene resin, a urethane resin, or
a silicone resin, or a mixture thereof.
19. The coating composition as claimed in claim 1, further
comprising a solvent selected from the group consisting of a
benzene compound, an ester, and a ketone, and a mixture thereof.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a coating composition. The
inventive composition can be applied to a substrate, particularly a
plastic substrate for optical applications, to enhance the hardness
of the substrate and prevent the substrate from being
scratched.
[0003] 2. Description of the Prior Art
[0004] Due to careless operations, the surfaces of substrates are
easily be scratched or worn, which adversely affects the appearance
and properties of the substrates. Particularly, optical substrates
are often impaired by the vibration during transportation.
Presently, the solution adopted in the industry is to adhere a
protective film to the surface of a substrate. Nevertheless, the
utilization of a protective film will increase the cost. To
overcome the above drawback, a helpful approach would be to apply a
coating to the surface of a substrate to enhance the hardness of
the substrate and prevent the surface of the substrate from being
scratched. In the past, UV curable resins were normally used as
scratch-resistant coatings because they can react in a short time
and achieve a degree of crosslinking. However, the utilization of
UV curable resins is limited by insufficient UV light transmission,
which may result in a non-cure or an incomplete cure. Moreover, due
to a crosslinking reaction, UV curable resins are subject to
inconsistent stresses or shrinkage rates and easy to warp or
crack.
[0005] In order to address the problems associated with the UV
light transmission and non-cure or incomplete cure in conventional
photo-curing techniques, and due to the fact that thermally curable
resins cure in a prolonged time, CN10106347A (US2007/0066698 A1)
discloses a dual cure composition which comprises at least one
filler, at least one curable monomer comprising at least one of an
ethylenic unit or cyclic ether unit or mixture thereof, at least
one photoinitiator; and at least one thermal initiator. CN10106347A
discloses exposing the dual cure composition to radiation to at
least partially photocure, and providing sufficient heat to
initiate thermal curing so as to obtain a cured composition.
[0006] U.S. Pat. No. 5,571,297 also discloses a dual cure binder
system to address the problems associated with conventionally used
phenolic resin that has excellent adhesion property but needs a
prolonged heating to achieve thermal curing, and to obviate the
above-mentioned drawbacks associated with the photocure. U.S. Pat.
No. 5,571,297 discloses a coated abrasive with a binder coat which
comprises a compound having at least one function that is radiation
curable and at least one function that is polymerizable under
thermally activated conditions to achieve the desired effects.
[0007] Incorporating a certain amount of a thermally curable resin
into a coating that contains a UV curable resin and utilize a dual
cure process to effectively generate a coating with a low degree of
crosslinking is already known in the art. For example, DE 19920799,
U.S. Pat. No. 4,025,407, and U.S. Pat. No. 6,835,759 have disclosed
such technique. Normally, the thermally curable resins used are
thermal setting resins. These thermal setting resins have a great
internal stress and cannot fully solve the problem associated with
warping. In addition, the curing of a thermal setting resin
normally requires a curing agent (or a crosslinker). However,
curing agents react with the thermal setting resin easily, thereby
increasing the molecular weight of the resin over time or resulting
in different extents of reaction, and changing the properties of
the resin. In this case, the resin should be consumed in a limited
period and is not suitable for long-time coating.
[0008] U.S. Pat. No. 6,835,759 discloses a coating composition
comprising a radiation curable component (a1), a thermally curable
binder component (a2), a thermally curable crosslinking compound
(a3), and optionally, one or more reactive diluents (a4) in a ratio
that is obtained by the following equation:
UV/TH=[a1+a4]NV/[a2+a3]NV. wherein [a1+a4]NV refers to the total
nonvolatile weight of components (a1) and (a4). and [a2+a3]NV
refers to the total nonvolatile weight of components (a2) and (a3).
In a preferred embodiment, when UV/TH is from 0.25 to 0.50, most
preferably from 0.30 to 0.45, the surface defects caused by
vaporous emissions can be reduced and a desirable adhesion,
particularly an especially desirable balance between porosity
sealing and adhesion, can be further obtained. However, when the
ratio UV/TH is within the above-mentioned ranges, the hardness and
thus the scratch resistance of the coating composition may not be
sufficient for practical applications.
[0009] Moreover, for easy processability, commonly used dual cure
resins have a lower glass transition temperature, which is normally
lower than 70.degree. C. Although the resins with a lower glass
transition temperature can be processes more easily, they exhibit
poor heat resistance. Compared with the resins with a lower glass
transition temperature, those with a higher glass transition
temperature are more stable and more heat resistant, particularly
when the resins are used in optical films or other components that
will be affected by the light or heat from a lamp. When the
temperature is up to 80.degree. C., the form of the material is
changed. Consequently, it is necessary to use the resins that have
a higher glass transition temperature and a better heat
resistance.
SUMMARY OF THE INVENTION
[0010] The present invention provides a coating composition
comprising:
[0011] (a) a thermal plastic resin selected from the group
consisting of a polycycloolefin resin, polyester resin,
polyacrylate resin, and a mixture thereof; and
[0012] (b) a radiation curable resin comprising: [0013] (b1) a
radiation polymer containing at least one mono- or multi-functional
acrylic acid based monomer as a polymerization unit; [0014] (b2) an
oligomer having an ethylenically unsaturated group; and [0015] (b3)
a photoinitiator, wherein the radiation curable resin is used in an
amount of 220-1000% by weight on the basis of the weight of the
thermal plastic resin.
[0016] The present invention selects thermal plastic resins as the
thermally curable resins, which can buffer stress and enhance the
adhesion of the radiation curable resin and provide the coating
composition with a better coating property, thereby enhancing the
processability of the resin and increasing the ratio of the amount
of the radiation curable resin so as to enhance the hardness of the
coating composition. When being applied to a substrate, the coating
composition of the present invention, once being cured, can enhance
the hardness of the substrate and prevent the substrate from being
scratched or impaired and impart the substrate with high
transparency without warping.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The thermal plastic resin used in the coating composition of
the present invention is selected from the group consisting of a
polycycloolefin resin; a polyester resin, such as poly(ethylene
naphthalate) (PEN); a polyacrylate resin, such as polymethyl
methacrylate (PMMA); and a mixture thereof, of which the
polyacrylate resin is preferred. The thermal plastic resin has at
least one functional group selected from the group consisting of
hydroxy, carboxy, amido, urethano, and epoxy, and a combination
thereof.
[0018] According to one embodiment of the present invention, a
polyacrylate resin is used as the thermal plastic resin, and the
polyacrylate resin contains a polymerization unit derived from the
monomer selected from the group consisting of acrylic acid,
methacrylic acid, methyl acrylate, methyl methacrylate, ethyl
acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate,
iso-butyl acrylate, iso-butyl methacrylate, iso-octyl acrylate,
iso-octyl methacrylate, cyclohexyl acrylate, cyclohexyl
methacrylate, glycidyl acrylate, glycidyl methacrylate,
hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl
acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,
2-hydroxypropyl methacrylate. and hydroxypropyl methacrylate and a
mixture thereof, among which acrylic acid. methacrylic acid, methyl
acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate,
iso-butyl acrylate, iso-butyl methacrylate, hydroxyethyl acrylate,
2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate, and a
mixture thereof are preferred.
[0019] The thermal plastic resin has a glass translation
temperature of greater than 80.degree. C., preferably from
80.degree. C. to 250.degree. C., and more preferably from
85.degree. C. to 130.degree. C.; and has an average molecular
weight in the range from 10.sup.4 to 2.times.10.sup.6, preferably
from 1.5.times.10.sup.4 to 3.times.10.sup.5, and more preferably
from 2.times.10.sup.4 to 6.times.10.sup.4.
[0020] The radiation curable resin according to the present
invention refers to a resin that can be cured upon being irradiated
with energetic rays. The energetic rays refer to a light source in
a certain wavelength range, such as UV light, infrared light,
visible light, or heat rays (nucleus rays or radiation rays), among
which UV light is preferred. The intensity of the irradiation is in
a range from 100 to 1000 mJ/cm.sup.2, preferably from 200 to 800
mJ/cm.sup.2.
[0021] The radiation curable resin used in the coating composition
of the present invention comprises a radiation polymer, an oligomer
having an ethylenically unsaturated group; and a photoinitiator.
The radiation polymer contains at least one mono- or
multi-functional acrylic acid based monomer as a polymerization
unit and the acrylic acid based monomer is an acrylic acid monomer
or an acrylate monomer. preferably an acrylate monomer. Suitable
acrylate monomers for the present invention include acrylate
monomers, methacrylate monomers, urethane acrylate monomers,
polyester acrylate monomers, and epoxy acrylate monomers, among
which acrylate monomers and methacrylate monomer are preferred.
[0022] The above-mentioned acrylate monomers can be selected from
the group consisting of methyl acrylate, methyl methacrylate, butyl
acrylate, 2-phenoxy ethyl acrylate, ethoxylated 2-phenoxy ethyl
acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, cyclic
trimethylolpropane formal acrylate, .beta.-carboxyethyl acrylate,
lauryl(meth)acrylate, isooctyl acrylate, stearyl(meth)acrylate,
isodecyl acrylate, isoborny(meth)acrylate, benzyl acrylate,
hydroxypivalyl hydroxypivalate diacrylate, ethoxylated
1,6-hexanediol diacrylate, dipropylene glycol diacrylate,
ethoxylated dipropylene glycol diacrylate, neopentyl glycol
diacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated
bisphenol-A di(meth)acrylate, 2-methyl-1,3-propanediol diacrylate,
ethoxylated 2-methyl-1,3-propanediol diacrylate,
2-butyl-2-ethyl-1,3-propanediol diacrylate, ethylene glycol
dimethacrylate, diethylene glycol dimethacrylate, 2-hydroxyethyl
methacrylate phosphate, tris(2-hydroxy ethyl)isocyanurate
triacrylate, pentaerythritol triacrylate, ethoxylated
trimethylolpropane triacrylate, propoxylated trimethylolpropane
triacrylate, trimethylolpropane trimethacrylate, pentaerythritol
tetraacrylate, ethoxylated pentaerythritol tetraacrylate,
ditrimethylolpropane tetraacrylate, propoxylated pentaerythritol
tetraacrylate, pentaerythritol tetraacrylate, dipentaerythritol
hexaacrylate, (meth)acrylate, hydroxyethyl acrylate (HEA),
2-hydroxyethyl methacrylate (HEMA), tripropylene glycol
di(meth)acrylate1,4-butanediol di(meth)acrylate, 1,6-hexanediol
di(meth)acrylate, allylated cyclohexyl di(meth)acrylate,
isocyanurate di(meth)acrylate, ethoxylated trimethylol propane
tri(meth)acrylate, propoxylated glycerol tri(meth)acrylate,
trimethylol propane tri(meth)acrylate, and
tris(acryloxyethyl)isocyanurate, and a mixture thereof.
[0023] To enhance the film formation of the coating composition,
the radiation curable resin according to the invention contains an
oligomer having an ethylenically unsaturated group that has a
molecular weight in the range from 10.sup.3 to 10.sup.4.
Preferably, the oligomers are acrylate oligomers, which include,
for example, but are not limited to, urethane acrylates, such as
aliphatic urethane acrylates, aliphatic urethane hexaacrylates, and
aromatic urethane hexaacrylates; epoxy acrylates, such as
bisphenol-A epoxy diacrylate and novolac epoxy acrylate; polyester
acrylates, such as polyester diacrylate; or homo-acrylates or a
mixture thereof.
[0024] The photoinitiators useful for the invention are those
generating free radicals upon photoirradiation to induce
polymerization through the transfer of free radicals. The
photoinitiators useful in the invention include, for example, but
are not limited to, benzophenone, benzoin,
2-hydroxy-2-methyl-1-phenylpropan-1-one,
2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy cyclohexyl phenyl
ketone, and 2,4,6-trimethylbenzoyl diphenyl phosphine oxide, and a
mixture thereof. Preferably, the photoinitiator is benzophenone or
1-hydroxy cyclohexyl phenyl ketone.
[0025] The present invention selects thermal plastic resins as the
thermally curable resins, which can buffer stress and enhance the
adhesion of the radiation curable resin and provide the coating
composition with a better coating property. thereby enhancing the
processability of the resin and increasing the ratio of the amount
of the radiation curable resin so as to enhance the hardness of the
coating composition. The suitable amount of the radiation curable
resin, as compared with the thermal plastic resin, depends on the
desired product to be obtained. In order to enhance the hardness of
the cured coating composition and to increase the scratch and wear
resistance of the cured coating composition for its application to
optical films without causing the films to warp, the radiation
curable resin is used in an amount of 220-1000% by weight,
preferably 250-500% by weight on the basis of the weight of the
thermal plastic resin.
[0026] In addition to the thermal plastic resin and radiation
curable resin. the coating composition of the present invention may
optionally comprise the additives conventionally known to persons
skilled in the art, which can be, for example, but are not limited
to, an anti-static agent, a solvent, a photoinitiator, diffusion
particles, a UV absorber, or inorganic particulates.
[0027] During the processing or fabrication of the coating
composition, static electricity will be generated by the friction
of the coating composition itself or between the coating
composition and other materials, which makes the free dusts in the
air aggregated on the surface, resulting in the damage of the
expensive electronic devices, and even causing a fire hazard due to
the ignition of the combustible gas or powder. Therefore, the
coating composition of the present invention may optionally
comprise an anti-static agent.
[0028] The anti-static agent can be directly incorporated into the
coating composition and the resultant composition is further mixed
and processed. The anti-static agent suitable for the present
invention is not particularly limited, and can be any anti-static
agent well known to persons having ordinary skill in the art, such
as ethoxy glycerin fatty acid esters, quaternary amine compounds,
aliphatic amine derivatives, epoxy resins (such as polyethylene
oxide), siloxane, or other alcohol derivatives, such as
poly(ethylene glycol) ester, poly(ethylene glycol) ether and the
like. Normally, a plastic material has a surface resistivity in the
range from 10.sup.15 to 10.sup.16 .OMEGA./.quadrature. (i.e.,
.OMEGA./m.sup.2). If an anti-static effect is desired, a surface
resistivity in the range from 10.sup.10 to 10.sup.12
.OMEGA./.quadrature. is preferred. However, when the surface
resistivity is higher than 10.sup.12 .OMEGA./.quadrature., the
anti-static effect is not good.
[0029] Optionally, the coating composition of the present invention
comprises a UV absorber. The UV absorber suitable for the present
invention can be any UV absorber well known to persons having
ordinary skill in the art, which includes, for example, a
benzotriazole, a benzotriazine, a benzophenone, or a salicylic acid
derivative. As an alternative, inorganic particulates that absorb
UV light, such as zinc oxide, zirconia, silicon dioxide, titanium
dioxide, alumina, calcium sulfate, barium sulfate, or calcium
carbonate, or a mixture thereof, can be used in the coating
composition. The particle size of the above-mentioned inorganic
particulates is normally in the range from 1 to 100 nm
(nanometers), preferably from 20 to 50 nm.
[0030] Optionally, the coating composition of the present invention
comprises diffusion particles. The diffusion particles suitable for
the present invention are well known to persons having ordinary
skill in the art, which include, for example, the organic particles
of an acrylate resin, a methacrylate resin, a styrene resin, a
urethane resin, or a silicone resin, or a mixture thereof.
[0031] Optionally, the coating composition of the present invention
comprises a solvent to improve the flowability of the composition
so that the coating composition can be applied to a substrate more
easily. The solvents useful for the present invention can be those
well known to persons having ordinary skill in the art, which
include, for example, a benzene compound, an ester, a ketone, or a
mixture thereof Non-limiting examples of the benzene solvent
include benzene, o-xylene, m-xylene, and p-xylene toluene, and a
mixture thereof. Non-limiting examples of the ester solvent include
ethyl acetate, butyl acetate, ethyl formate, methyl acetate.
ethoxyethyl acetate, ethoxypropyl acetate, and monomethyl ether
propylene glycol acetate, and a mixture thereof. Non-limiting
examples of the ketone solvent include acetone, methyl ethyl
ketone, and methyl isobutyl ketone, and a mixture thereof.
[0032] The amounts in weight percentage of the components of the
inventive coating composition are not particularly limited, and
preferably, are as follows: thermal plastic resin: 10-40%;
radiation curable resin: 20-70%; anti-static agent: 3-5%; inorganic
particulates: 0-16%; diffusion particles: 0-35%; solvent: 10-40%.
The amounts in weight percentage of the components of the radiation
curable resin are as follows: radiation polymer: 15-45% on the
basis of the weight of the radiation curable resin; oligomer having
an ethylenically unsaturated group: 30-50% on the basis of the
weight of the radiation curable resin; photoinitiator: 2-10% on the
basis of the weight of the radiation curable resin.
[0033] The coating composition of the present invention can be
applied to the surface of a substrate by coating or adhesion,
preferably by coating. The substrate is not particularly limited
and the examples thereof include ceramic tile, wood, leather,
stone, glass, metals, paper, plastic, fiber, cotton fabric, home
appliance, lighting device, or computer case. Preferably, the
substrate is a glass or plastic substrate, particularly the glass
or plastic substrates for optical applications. According to an
embodiment of the present invention, the inventive coating
composition can be applied to light source devices, such as,
advertising light boxes or flat panel displays, particularly the
panel devices or backlight modules of liquid crystal displays
(LCD), by a coating or adhesion method, preferably by a coating
method, so as to form a scratch resistant layer on the surface of
the substrate. When the inventive coating composition is applied to
an optical substrate, the surface of the resultant coated substrate
is flat without warp, so that the optical properties will not be
adversely influenced.
[0034] The above-mentioned plastic substrate is not particularly
limited and can be, for example, a polyester resin, such as
polyethylene terephthalate (PET) or polyethylene naphthalate (PEN);
a polyacrylate resin, such as polymethyl methacrylate (PMMA);
polyimide resin; a polycycloolefin resin; a polycarbonate resin; a
polyurethane resin; triacetate cellulose (TAC); or polylactic acid
(PLA) fiber or a mixture thereof. The preferred substrates are
those formed from polyethylene terephthalate, polymethyl
methacrylate, polycycloolefin resin, or triacetate cellulose. or a
mixture thereof. More preferably, the substrate is polyethylene
terephthalate. The thickness of the substrate typically depends on
the requirement of the desired optical product, and is preferably
in a range from about 16 .mu.m to about 350 .mu.m.
[0035] The coating composition of the present invention can be
cured by a dual cure method with both radiation and heat. By this
dual cure, the warping problem associated with the coated substrate
caused by an extremely great internal stress due to a rapid curing
can be avoided as the shrinkage rate can be effectively controlled.
The coating composition of the present invention exhibits the
properties of high strength, good toughness, heat resistance, and
high hardness, and has a pencil hardness of 3H or more as measured
according to JIS K5400 standard method.
[0036] The coating composition of the present invention can be
prepared by mixing the above-mentioned components in a suitable
ratio in, for example, an agitator, a dissolver, a homogenizer, or
a dispersion mixer.
[0037] The coating composition of the present invention can be
cured by any curing method well known to persons having ordinary
skill in the art, in which the order of the curing with radiation
and the curing with heat is not particularly limited. For example,
a coating composition containing the above-mentioned components is
prepared and provided with sufficient heat. Alternatively, the
coating composition can be applied to a substrate mentioned above,
and the coated substrate is provided with sufficient heat. If the
coating composition contains a solvent, the coating composition or
the coated substrate can be put into an oven to evaporate the
solvent, and is heated to a temperature higher than the glass
transition temperature of the thermal plastic resin and heated at
such temperature for several minutes to cure the composition.
Thereafter, the coating composition or the coated substrate is
exposed to the energetic rays from a radiation source to result in
a radiation polymerization. Suitable radiation sources include UV
light, visible light, and high energy rays (electron beam), among
which UV light is preferred. The intensity of the energetic rays is
in the range from 200 to 800 mJ/cm.sup.2.
[0038] According to another embodiment of the present invention,
the above-mentioned coating composition or coated substrate is
first exposed to the energetic rays from a radiation source to
result in a radiation polymerization. The intensity of the
energetic rays is in the range from 200 to 800 mJ/cm.sup.2.
Thereafter, a sufficient amount of heat is provided to the coating
composition or coated substrate to heat the coating composition or
coated substrate to a temperature higher than the glass transition
temperature of the thermal plastic resin, and the coating
composition or coated substrate is heated at such temperature for
several minutes.
[0039] If desired, the above-described steps can be repeated to
afford a multi-layered coating.
[0040] The following examples are used to further illustrate the
present invention, but not intended to limit the scope of the
present invention.
PREPARATION EXAMPLE 1
[0041] Formulating radiation curable resin formulation A: In a 250
mL glass bottle, 15 g ethyl acetate was added. With high speed
stirring, the following acrylate monomers: 10 g dipentaerythritol
hexaacrylate, 2 g trimethylol propane trimethacrylate, 14 g
pentaerythritol triacrylate, and an oligomer: 34.5 g of an
aliphatic urethane hexaacrylate [Etercure 6415-100, Eternal Co.],
and a photoinitiator: 4.5 g 1-hydroxy cyclohexyl phenyl ketone were
added in sequence to provide 100 g of radiation curable resin
formulation A with a solids content of about 80%.
EXAMPLE 1
The Amount of Radiation Curable Resin (24.86.times.80%) is 220 wt %
on the Basis of the Amount of Thermal Plastic Resin
(30.14.times.30%)
Preparation of Scratch-Resistant Layer
[0042] To a 250 ml glass bottle, 25 g ethyl acetate was added as a
solvent. With high speed stirring, the following substances were
added in sequence: 24.86 g of the radiation curable resin
formulation A prepared in Preparation Example 1 (with a solids
content of about 80%, Eternal Company); a thermal plastic resin:
30.14 g of polymethacrylic polyol resin [Eterac 7365-s-30, Eternal
Company] (with a solids content of about 30%, and a glass
transition temperature Tg of 95.degree. C.); and 4.2 g of an
anti-static agent [GMB-36M-AS, Marubishi Oil Chem. Co., Ltd] (with
a solids content of about 20%) to prepare a coating composition
with a total weight of about 85 g and solids content of about 30%.
The coating composition was coated on a PET substrate of 188 .mu.m
in thickness with a RDS Bar Coater #8, dried at 100.degree. C. for
1 minute, then dried by being exposed in a UV exposure machine
[Fusion UV, F600V, 600 W/inch, H type lamp source] at a power set
at 100%, at a speed of 15 m/m in with an energetic ray of 250
mJ/cm.sup.2, and at room temperature for 4 seconds, to afford a
scratch-resistant layer with a coating thickness of about 6 .mu.m.
The scratch-resistant layer was tested for various properties, and
the test results obtained are shown in Table 1 below.
EXAMPLE 2
The Amount of Radiation Curable Resin (29.12.times.80%) is 300 wt %
on the Basis of the Amount of Thermal Plastic Resin
(25.88.times.30%)
Preparation of Scratch-Resistant Layer
[0043] To a 250 ml glass bottle, 25 g ethyl acetate was added as a
solvent. With high speed stirring, the following substances were
added in sequence: 29.12 g of the radiation curable resin
formulation A prepared in Preparation Example 1 (with a solids
content of about 80%, Eternal Company); a thermal plastic resin:
25.88 g of polymethacrylic polyol resin [Eterac 7365-s-30, Eternal
Company] (with a solids content of about 30%, and a glass
transition temperature Tg of 95.degree. C.); and 4.2 g of an
anti-static agent [GMB-36M-AS, Marubishi Oil Chem. Co., Ltd] (with
a solids content of about 20%) to prepare a coating composition
with a total weight of about 85 g and solids content of about 30%.
The coating composition was coated on a PET substrate of 188 .mu.m
in thickness with a RDS Bar Coater #8, dried at 110.degree. C. for
1 minute, then dried by being exposed in a UV exposure machine
[Fusion UV, F600V, 600 W/inch, H type lamp source] at a power set
at 100%, at a speed of 15 m/min with an energetic ray of 250
mJ/cm.sup.2, and at room temperature for 4 seconds, to afford a
scratch-resistant layer with a coating thickness of about 6 .mu.m.
The scratch-resistant layer was tested for various properties, and
the test results obtained are shown in Table 1 below.
EXAMPLE 3
The Amount of Radiation Curable Resin (38.08.times.80%) is 600 wt %
on the Basis of the Amount of Thermal Plastic Resin
(16.92.times.30%)
Preparation of Scratch-Resistant Layer
[0044] To a 250 ml glass bottle, 25 g ethyl acetate was added as a
solvent. With high speed stirring, the following substances were
added in sequence: 38.08 g of the radiation curable resin
formulation A prepared in Preparation Example 1 (with a solids
content of about 80%, Eternal Company); a thermal plastic resin:
16.92 g of polymethacrylic polyol resin [Eterac 7365-s-30, Eternal
Company] (with a solids content of about 30%, and a glass
transition temperature Tg of 95.degree. C.); and 4.2 g of an
anti-static agent [GMB-36M-AS, Marubishi Oil Chem. Co., Ltd] (with
a solids content of about 20%) to prepare a coating composition
with a total weight of about 85 g and solids content of about 33%.
The coating composition was coated on a PET substrate of 188 .mu.m
in thickness with a RDS Bar Coater #8, dried at 110.degree. C. for
1 minute, then dried by being exposed in a UV exposure machine
[Fusion UV, F600V. 600 W/inch, H type lamp source] at a power set
at 100%, at a speed of 15 m/min with an energetic ray of 250
mJ/cm.sup.2, and at room temperature for 4 seconds, to afford a
scratch-resistant layer with a coating thickness of about 6 .mu.m.
The scratch-resistant layer was tested for various properties, and
the test results obtained are shown in Table 1 below.
EXAMPLE 4
The Amount of Radiation Curable Resin (41.25.times.80%) is 800 wt %
on the Basis of the Amount of Thermal Plastic Resin
(13.75.times.30%)
Preparation of Scratch-Resistant Layer
[0045] To a 250 ml glass bottle, 25 g ethyl acetate was added as a
solvent. With high speed stirring, the following substances were
added in sequence: 41.25 g of the radiation curable resin
formulation A prepared in Preparation Example 1 (with a solids
content of about 80%, Eternal Company); a thermal plastic resin:
13.75 g of polymethacrylic polyol resin [Eterac 7365-s-30, Eternal
Company] (with a solids content of about 30%, and a glass
transition temperature Tg of 95.degree. C.); and 4.2 g of an
anti-static agent [GMB-36M-AS, Marubishi Oil Chem. Co., Ltd] (with
a solids content of about 20%) to prepare a coating composition
with a total weight of about 85 g and solids content of about 38%.
The coating composition was coated on a PET substrate of 188 .mu.m
in thickness with a RDS Bar Coater #8, dried at 110.degree. C. for
1 minute, then dried by being exposed in a UV exposure machine
[Fusion UV, F600V, 600 W/inch, H type lamp source] at a power set
at 100%, at a speed of 15 m/min with an energetic ray of 250
mJ/cm.sup.2, and at room temperature for 4 seconds, to afford a
scratch-resistant layer with a coating thickness of about 6 .mu.m.
The scratch-resistant layer was tested for various properties, and
the test results obtained are shown in Table 1 below.
COMPARATIVE EXAMPLE 1
[0046] A commercially available protective diffusion film with a
thickness of 195 .mu.m and having organic particles with a particle
size distribution from 1 to 10 .mu.m in the diffusion layer on the
substrate surface [PBS632L, Keiwa Co.] was tested for various
properties, and the results obtained are shown in Table 1
below.
COMPARATIVE EXAMPLE 2
[0047] A commercially available protective diffusion film with a
thickness of 200 .mu.m and having polymethyl methacrylate particles
with a particle size distribution from 1 to 20 .mu.m in the
diffusion layer on the substrate surface [D117VGZ, Tsujiden Co.]
was tested for various properties, and the results obtained are
shown in Table 1 below.
COMPARATIVE EXAMPLE 3
[0048] A commercially available protective diffusion film with a
thickness of 205 .mu.m and having organic particles with a particle
size distribution from 1 to 10 .mu.m in the diffusion layer on the
substrate surface [PBS072, Keiwa Co.] was tested for various
properties, and the results obtained are shown in Table 1
below.
Test Method A:
[0049] Film Thickness Test: The thicknesses of the films of
Examples 1 to 4 and Comparative Examples 1 to 3 were measured with
a coating thickness gauge (PIM-100, TESA Corporation) under 1 N
pressing contact. The results were recorded above.
Testing Method B:
[0050] Pencil Hardness Test: According to JIS K-5400 method, the
surfaces of the test samples (for the comparative examples, the
scratch-resistant layers on the backside of the substrate) were
tested with a Pencil Hardness Tester [Elcometer 3086, SCRATCH BOY],
using Mitsubishi pencil (2H and 3H). The results of the tests are
shown in Table 1 below.
[0051] Surface Resistivity Test: The surface resistivity of the
surfaces of the samples (for the comparative examples, the
scratch-resistant layers on the backside of the substrate) was
measured with a Superinsulation Meter [EASTASIA TOADKK Co.,
SM8220&SME-8310, 500 V]. The testing conditions were:
23.+-.2.degree. C., 55.+-.5% RH. The results of the test are shown
in Table 1 below.
[0052] Wear Resistance Test: A Linear Abraser [TABER 5750] was
used, and a 3M BEF-III-10T film (20 mm length.times.20 mm width) to
be tested was affixed on a 300 g platform (area: 20 mm
length.times.20 mm width). The prism structure layer of the film
faced upwards, so as to test the wear resistance under high
pressure of the scratch-resistance layers of films under the test.
The wear resistance test was performed in 10 cycles/min with a test
path of 2 inches and a speed of 10 cycles/min. The results of the
test are listed in Table 1 below.
[0053] Warp Test: The test films were cut into level films with 100
mm length.times.100 mm width, placed in an oven at 120.degree. C.
for 10 min, and then taken out and left at room temperature (for
the comparative examples, the scratch-resistant layers on the
backside of the substrate faced upwards). After being cooled down
to the room temperature, the films were measured for warping level
on the four corners with a gap gauge (recording unit: millimeter
(mm), recording manner: for example, 0,0:0;0). and thereby, the
test samples were evaluated for heat resistance and warp resistance
properties. The results of the test are listed in Table 1
below.
TABLE-US-00001 TABLE 1 Comparative Comparative Comparative Example
1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3
Pencil Hardness 3H 3H 3H 3H 2H 2H 3H (scratch-resistant layer)
Surface Resistivity .OMEGA./.quadrature. 3.10 .times. 10.sup.11 7.3
.times. 10.sup.10 6.19 .times. 10.sup.11 3.39 .times. 10.sup.11 1.3
.times. 10.sup.12 1.8 .times. 10.sup.12 2.6 .times. 10.sup.16
(scratch-resistant layer) Wear Resistance Test of No Scratch No
Scratch No Scratch No Scratch Severe Scratch Light Scratch Severe
Scratch Scratch-Resistant Layer Warp Test (mm) 0; 0; 0; 0 0; 0; 0;
0 0; 0; 0; 0 0; 0; 0; 0.1 0.1; 0; 0.1; 0.1 0.1; 0.1; 0.1; 0.1 0; 0;
0; 0 (120.degree. C., 10 min)
[0054] According to the results of the examples and the comparative
examples shown in Table 1, the scratch-resistant films according to
the present invention possess good anti-static property and high
hardness property and have preferred surface evenness without
warping.
* * * * *